1,102 research outputs found
Advanced monitoring of South Portugal water bodies towards WFD
The challenge on implementation of the EU Water Framework Directive (WFD) fosters the
development of new monitoring methods and approaches. It is now commonly accepted that
the use of classical monitoring campaigns in discrete point is not sufficient to fully assess and
describe a water body. Due to this the WFD promote the use of modelling techniques in
surface waters to assist all phases of the process, from characterisation and establishment of
reference conditions to identification of pressures and assessment of impact. The work
presented in this communication is based on these principles. A classical monitoring of the
water status of the main transitional water bodies of Algarve (south of Portugal) is combined
with advanced in situ water profiling and hydrodynamic, water quality and ecological
modelling of the systems to build a complete description of its state. This approach extends
spatially and temporally the resolution of the classical point sampling. The methodology was
applied during a 12 month program in Ria Formosa coastal lagoon, the Guadiana estuary and
the Arade estuary. The synoptic profiling uses an YSI 6600 EDS multi-parameter system
attached to a boat and a GPS receiver to produce monthly synoptic maps of the systems. This
data extends the discrete point sampling with laboratory analysis performed monthly in
several points of each water body. The point sampling is used to calibrate the profiling system
and to include variables, such as nutrients, not measured by the sensors. A total of 1427
samplings were performed for physical and chemical parameters, chlorophyll and
microbiologic contamination in the water column. This data is used to drive the
hydrodynamic, transport and ecological modules of the MOHID water modelling system
(www.mohid.com), enabling an integrate description of the water column
Improving search engines with open Web-based SKOS vocabularies
Dissertação para obtenção do Grau de Mestre em Engenharia InformáticaThe volume of digital information is increasingly larger and even though organiza-tions are making more of this information available, without the proper tools users have great difficulties in retrieving documents about subjects of interest. Good infor-mation retrieval mechanisms are crucial for answering user information needs.
Nowadays, search engines are unavoidable - they are an essential feature in docu-ment management systems. However, achieving good relevancy is a difficult problem particularly when dealing with specific technical domains where vocabulary mismatch problems can be prejudicial. Numerous research works found that exploiting the lexi-cal or semantic relations of terms in a collection attenuates this problem.
In this dissertation, we aim to improve search results and user experience by inves-tigating the use of potentially connected Web vocabularies in information retrieval en-gines. In the context of open Web-based SKOS vocabularies we propose a query expan-sion framework implemented in a widely used IR system (Lucene/Solr), and evaluated using standard IR evaluation datasets.
The components described in this thesis were applied in the development of a new search system that was integrated with a rapid applications development tool in the context of an internship at Quidgest S.A.Fundação para a Ciência e Tecnologia - ImTV research project, in the context of the UTAustin-Portugal collaboration (UTA-Est/MAI/0010/2009); QSearch project (FCT/Quidgest
Temporal Information Models for Real-Time Microblog Search
Real-time search in Twitter and other social media services is often biased
towards the most recent results due to the “in the moment” nature of topic
trends and their ephemeral relevance to users and media in general. However,
“in the moment”, it is often difficult to look at all emerging topics and single-out
the important ones from the rest of the social media chatter. This thesis proposes
to leverage on external sources to estimate the duration and burstiness of live
Twitter topics. It extends preliminary research where itwas shown that temporal
re-ranking using external sources could indeed improve the accuracy of results.
To further explore this topic we pursued three significant novel approaches: (1)
multi-source information analysis that explores behavioral dynamics of users,
such as Wikipedia live edits and page view streams, to detect topic trends
and estimate the topic interest over time; (2) efficient methods for federated
query expansion towards the improvement of query meaning; and (3) exploiting
multiple sources towards the detection of temporal query intent. It differs from
past approaches in the sense that it will work over real-time queries, leveraging
on live user-generated content. This approach contrasts with previous methods
that require an offline preprocessing step
EU water framework directive: will the nitrate load reduction from diffuse sources produce the same results in all estuaries?
The impact of urban waste-water and non-point nitrate discharges in estuarine and near-shore
coastal waters are analyzed. The study is focused on the effects of applying the European directives
91/271/EEC and 91/676/EEC to these systems. 4 Portuguese estuaries and two coastal lagoons with different
characteristics are studied. A modelling system is applied and calibrated in each system. Three nitrate load
scenarios are examined. It is shown that the morphologic and hydrodynamic characteristics of the domain
largely control the ecological processes in these systems. The primary production limitation factors are split
into “biologic” and “hydrodynamic” components. The physical limitation due to hydrodynamic and residence
time is the most important factor. The combined limitation of “biologic” factors (temperature, light and nutrients
availability) control productivity only in the systems where physical limitation is not important
Modelação ecológica no estuário do Sado
Os modelos matemáticos são ferramentas poderosas para avaliar o impacto humano em sistemas costeiros e estuarinos de estrutura complexa. Neste artigo utiliza-se um sistema de modelos matemáticos para simular o comportamento hidrodinâmico e biológico do estuário do Sado. Estudos experimentais de análise da evolução da biomassa de fitoplâncton durante os últimos 10 anos indicam que o ecossistema se encontra numa situação relarivamente estável, exibindo pouca tendência para a eutrofização (Cabeçadas, 1993). Neste Artigo procura-se caracterizar o estado trófico do sistema, confirmar as conclusões obtidas experimentalmente e interpretar os processos que ocorrem na região do estuário
Modelação do transporte vertical no estuário do Sado em condições barotrópicas
Em estuários barotrópicos podem-se desenvolver importantes escoamentos tridimensionais devido à interacção da maré com a batimetria. O estuário do Sado encontra-se nessas condições porque se pode considerar barotrópico durante praticamente todo o ano e possui uma batimetria com forte curvatura e gradientes elevados. Um modelo tridimensional de equações primitivas é utilizado para caracterizar os escoamentos tridi- mensionaís no estuário e a sua correlação com as características da batimetria. A importância destes escoamentos para o transporte vertical de substâncias biogeoquímicas é investigada utilizando um modelo de qualidade da água tridimensional do tipo Euleriano
Combining sampling, profiling, remote sensing and modelling to efficiently monitoring estuarine and coastal water quality
Monitoring of coastal and estuarine water quality has been traditionally performed by
sampling with subsequent laboratory analysis. This has the disadvantages of low spatial
and temporal resolution and high cost. In the last decades two alternative techniques
have emerged to overcome this drawback: profiling and remote sensing. Profiling using
multi-parameter sensors is now in a commercial stage. It can be used, tied to a boat, to
obtain a quick “picture” of the system. The spatial resolution thus increases from single
points to a line coincident with the boat track. The temporal resolution however remains
unchanged since campaigns and resources involved are basically the same. The need for
laboratory analysis was reduced but not eliminated because parameters like nutrients,
microbiology or metals are still difficult to obtain with sensors and validation
measurements are still needed. In the last years the improvement in satellite resolution
has enabled its use for coastal and estuarine water monitoring. Although spatial
coverage and resolution of satellite images in the present is already suitable to coastal
and estuarine monitoring, temporal resolution is naturally limited to satellite passages
and cloud cover. With this panorama the best approach to water monitoring is to
integrate and combine data from all these sources. The natural tools to perform this
integration are numerical models. Models benefit from the different sources of data to
obtain a better calibration. After calibration they can be used to extend spatially and
temporally the methods resolution. In Algarve (South of Portugal) a monitoring effort
using this approach is being undertaken. The monitoring effort comprises five different
locations including coastal waters, estuaries and coastal lagoons. The objective is to
establish the base line situation to evaluate the impact of Waste Water Treatment Plants
design and retrofitting. The field campaigns include monthly synoptic profiling, using
an YSI 6600 multi-parameter system, laboratory analysis and fixed stations. The remote
sensing uses ENVISAT\MERIS Level 2 Full Resolution data. This data is combined
and used with the MOHID modelling system to obtain an integrate description of the
systems. The results show the limitations of each method and the ability of the
modelling system to integrate the results and to produce a comprehensive picture of the
system
Qualidade da água na Ria Formosa: combinando técnicas de amostragem e de modelação para uma gestão integrada das águas residuais
Aplica-se uma técnica combinada de amostragem clássica, perfilagem in situ com
sonda multiparamétrica e modelação matemática para avaliar a qualidade da água da
Ria Formosa como meio receptor dos efluentes das ETAR’s. O sistema de modelação
desenvolvido baseia-se num modelo hidrodinâmico que resolve as equações de águas
pouco profundas pelo método dos volumes finitos acoplado a um modelo de transporte
Lagrangiano para a simulação das plumas microbiológicas. Este sistema é usado como
ferramenta de gestão para ensaiar diferentes cenários de descarga com variação da
localização do ponto de descarga, analisando o impacto das alternativas no meio
receptor
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